A novel wideband active feedback amplifier linearization scheme suitable for handsets

A new active feedback network is proposed for reducing intermodulation distortion (IMD). It is based on using the existing second harmonic zone (SHZ) distortion energy generated by the amplifier to predistort the input signals optimally to obtain a linear output. The technique is analyzed theoretically and practical results demonstrate the linearization performance. The measured two-tone test showed 23-dB reduction in the third-order intermodulation products (IMP/sub 3/), where /spl pi//4 DQPSK and W-CDMA gave up to 15-dB and 13-dB adjacent channel interference (ACI) suppression respectively. This technique differs from available active feedback techniques by performing both with narrow and wideband modulated signals. The linearization circuitry is simple and small in size.